Utility companies face ongoing challenges with consistently satisfying the demand for electricity. Facilities for generating electricity are typically well-suited for supplying constant amounts of electricity. However, consumers' demand for electricity is often quite the opposite in that the aggregate electricity demand varies significantly over the course of the delay. The daily variance results in one or more ‘peak’ demand times or periods in which demand on the utility company is greatest, and ‘non-peak’ demand times or periods in which demand on the utility company is reduced.
The variance in demand over the course of a day may be impacted by a number of factors such as weather and living patterns. For example, during the summertime, demand generally tends to increase as the outside temperature increases to levels considered uncomfortable as consumers increase their usage of high consumption appliances such as air conditioning systems. Demand also generally tends to vary based on work habits, where demand peaks when people leave for work and again when people return from work. During some points in the year, such as during extremely hot days, demand may reach extreme peaks.
Utility companies have a variety of options for dealing with the variable demand for energy. They may, for example, increase their ability to satisfy higher peak demands by building additional power plants. However, the costs of doing so are often prohibitive and building such plants is often inefficient as the added capacity is used for only short durations throughout the year. They may buy additional capacity from other utility company's or energy providers, but doing so is also costly as such company's may charge a premium and the energy transfer from those other companies is often less efficient. Instead of increasing supply, utility companies may also address peak demands by reducing the demand via load shedding.
Load shedding is a technique in which the utility company reduces the amount of energy demanded by its consumers during a period of peak demand. A variety of load shedding techniques are in use today, most of which are based on the utility company directly controlling the cooling systems of its consumers. During such peak demand periods the utility company controls the cooling systems to reduce their energy demand. Such events, which most often take place on very hot days in the mid-to-late afternoon and have a duration in the general range of two to six hours, are referenced in the literature by a variety of different names such as load shedding events, load shifting events, and demand response events. The goal of the utility company in carrying out such events is not necessarily to reduce the total amount of energy consumed over the whole day, but rather to reduce the peak demand during that particular two-to-six hour interval, i.e., during the load shedding interval or demand-response interval. Typically, the end result is that the energy that would have been consumed during the load shedding interval is instead consumed in the hours subsequent to the load shedding interval, as the cooling systems of the participating homes work to regain their cooler normal setpoint temperature. Such control, of course, often creates an inconvenience to the consumers who sign up to participate in such a ‘demand response program’ as their cooling system may not cool their residence as expected. However, in return for this inconvenience the consumer is often granted certain benefits, such as more favorable rates for energy consumed outside of the peak demand period.
One common load shedding technique, often referred to as direct load control, involves the periodic on-and-off cycling of power to the cooling system of each participating customer under the direct control of the utility during the load shedding period. In such a method, a remotely controllable switch is installed on the cooling system of each customer and is operable to disconnect power to the cooling system under the direct control of the utility company. The power to the cooling system may then be directly controlled by the utility company such that it is turned off for regular, fixed time intervals during a peak demand period. Consumers may express some degree of animosity towards such a technique, however, as direct load control results in a lack of control by the consumer of their cooling system, and often results in inside temperatures that are found to be uncomfortable by the consumer. Deficiencies in the communication link between the utility company and the switch can worsen the problem, with lost commands from the utility company to the switch to reconnect power to the cooling system resulting in the cooling system undesirably remaining in a disconnected state. Such problems have resulted in some consumers attempting to obviate the control on their cooling system while still attaining the benefits of participating in the demand response program by bypassing the remotely controlled switch. As a result, while such “cheaters” may acquire their desired individual cooling system control, the effectiveness of the overall demand response program can be undermined.
Another known load shedding technique involves remote control of the setpoint temperature of the thermostat of each participating customer by the utility, wherein the utility sends a common setback value to the thermostats of the participating customers. During the load shedding period, the participating thermostats will control the indoor temperature to a temperature setpoint value that is higher than the normally scheduled temperature setpoint value by the setback amount. This control by the utility company will typically result in an ambient temperature that is less comfortable than what the consumers would have otherwise experienced, but provides the benefit of both energy and cost savings. While providing the potential for increased comfort and acceptance over direct on/off cycling of the power to the cooling system by the utility, this technique can have disadvantages including lack of control by the consumer and the utility company's ability to set the setback value to any value the utility company deems suitable. Moreover, the use of a single setback value for all consumers fails to recognize differences in perceptions in comfort, differences in thermal characteristics of residences, differences in cooling capacities of the cooling systems, and other differences among the base of participating customers.
U.S. Patent Publication No. 2012/0053745 to Howard Ng discusses a system and method for establishing load control during a load shedding event. Specifically, Ng discusses a technique that allows a customer or utility to control a maximum temperature rise under a direct load control program. The customer may set a comfort range on their thermostat that indicates a range of temperatures from a desired temperature that the customer is comfortable with. During a load shedding event, in a hot weather example, a switch on a space conditioning load is activated so that the space conditioning load undergoes direct load control (i.e., fixed-width duty cycling). The space conditioning load undergoes direct load control until the indoor temperature exceeds the upper value of the comfort range, at which point control will be transferred from direct load control to temperature setback control.
Although the above-mentioned load shedding methods offer utility companies options to address peak energy demands, the tools to do so are limited. What are needed are user interfaces that are intuitive, offer flexibility in managing demand response events, and relatively informative as to how much energy will be shifted in a demand response event so that utility companies can better manage demand response events.